Okay, so it sounds like a CF5 will fit, but some attachments are impossible as they come from the factory. Is that right?
To pressure ferment, you need a spunding valve (to control the amount of pressure) and a pressure release valve (for safety). I guess technically you just need a spunding valve but if it were to get stuck and pressure builds you could create a bomb. I use Spikes all-in-one which does both.So no pressure brewing without that big valve.